A volumetric 3D display displays 3D images in a real 3D space. Each “voxel” in a volumetric image locates actually and physically at the spatial position where it is supposed to be, and light rays travel directly from that position toward omni-directions to form a real image in the eyes of viewers. As a result, a volumetric display possesses all major elements in both physiological and psychological depth cues and allows 360° walk-around viewing by multiple viewers without the need of special glasses.
For example, Tsao in Japanese patent application publication no. P2002-268136A describes a volumetric 3D (V3D) display that a “rotary reciprocating” mechanism drives a flat panel display to create volumetric 3D images directly, as illustrated in FIG. 1, in side view. The flat panel display is mounted on a support structure 520. Two pairs of rotary arms, 510a and 510c, drive the flat panel display and the support structure in a rotary motion such that the flat panel display rotates about an axis but with its surface always facing a fixed direction. As a result, the display panel sweeps a display space 12 as if in a reciprocating motion. The moving display panel distributes frames of 2D images in the display space and forms V3D images by after-mage effect.
Another category of V3D displays uses a moving screen and projecting 2D images on the screen. FIG. 2 illustrates such a system. It has three major portions: a rotary reciprocating screen unit 1511 (comprising a screen 11 mounted on rotary arms 1522); a high frame rate image projection system 15; and an optical interfacing mechanism 13 (comprising a single reflector 1321 mounted on rotary arms 1322). The screen 11 and the reflector 1321 are driven by two rotary reciprocating mechanisms, similar to the mechanism of FIG. 1, respectively. The reflector 1321, called interfacing reflector moves in synchronization with the screen but at a linear speed of ½ of the speed of the screen. The projection path is from the projector 15 to the interfacing reflector 1321, then to the folding reflector 1502 and then to the screen. This projection path length is kept constant as the screen and the interfacing reflector rotate. The high-frame-rate projector projects a set of 2D image frames onto the moving screen. Details and variations of the system are described in Tsao U.S. Pat. No. 6,765,566 B1 (See FIG. 20 of the referred patent) and Tsao U.S. Pat. No. 6,302,542 (See FIGS. 2a, 4b and 5b and the specification of the referred patent)
One issue of a V3D display is the limit of psychological visual depth. The display space has a finite size and therefore the physiological visual depth is limited. In contrast, a 2D display can display basically an infinite depth by psychological cues in the form of perspective view.
This invention is to describe methods of displaying both physiological and psychological depth cues in a volumetric image display. This added psychological visual depth can display a background image of infinite depth and is useful in applications such as flight simulation or in gaming.